This invention relates generally to chemical oxygen generators for civilian and military airplanes to provide supplemental oxygen, and more particularly relates to a chemical oxygen generator having a chemical oxygen generating core assembly composed of multiple sections, with at least two of the sections arranged in parallel so that a duration of operation of the chemical oxygen generator can be extended without increasing the length of the generator.
Chemical oxygen generators are typically used in situations requiring the generation of supplemental oxygen, such as in aviation and in submarines, for example, and in other similar settings where it is useful to furnish a convenient and reliable supply of oxygen gas of breathable quality. Chemical oxygen generating compositions based upon the decomposition of alkali metal chlorates or perchlorates have long been used as an emergency source of breathable oxygen in passenger aircraft, for example.
An aircraft oxygen generator is commonly preprogrammed according to the descent profile of a given type of airplane, and must meet the minimum oxygen flow requirement at all times during a descent. When the oxygen generating reaction is initiated at one end of the core, the reaction front propagates along the longitudinal axis toward the other end of the core as oxygen is generated. Ideally, the reaction zone moves at a steady, repeatable rate governed by the amounts of fuel and catalyst incorporated at a given point along the length of the core. Once initiated, a reaction front moves from the ignition end to the outlet end of the generator, producing oxygen.
One conventional chemical oxygen generator is known that includes an oxygen generating candle having a chemical core with a slightly tapered cylindrical shape. Once initiated, the candle will sustain decomposition to release breathable oxygen until the candle is completely reacted. However, since the reaction front needs to move at a certain linear rate, the length of the chemical core has to be increased when a relatively longer duration of operation is needed. Due to the limited space available in aircraft, it is difficult to increase the generator length beyond the length of the typical space envelope provided for an oxygen generator, so that heavier cores are typically used in such conventional chemical oxygen generators to insure the chemical cores have sufficient duration.
One known chemical oxygen generator includes an elongate rigid thermal insulating section, and a conduit section on one side of the rigid section providing multiple gas flow paths for conducting released oxygen from a burning candle along the plate for increasing the burning action of the burning portion of the candle and pre-heating the unburned portion of the candle. A plurality of the plates are combined to form a honeycomb type separator assembly made from interlocking ceramic plates for surrounding a candle, and a number of such separator assemblies are combined to form a multi-candle oxygen generator for oxygen supply flow profiles that require a high initial flow rate. The honeycomb type separator occupies a substantial volume and increases weight of the chemical candle, and is not suitable for aviation use.
In order for the oxygen generating reaction in a chemical oxygen generator to remain sufficiently stable that the reaction is not extinguished, the reaction front must move with a sufficiently high linear velocity. If the reaction front moves too slowly, the reaction becomes less controllable, and may stop. In order to maintain a minimum reaction front linear velocity and meet requirements for a duration of operation of the chemical oxygen generator, typically it has been necessary to increase the weight or length of the chemical core of the chemical oxygen generator, resulting in an increase in the weight or length of the chemical oxygen generator. Some aircraft may require a very long duration, while requiring a high flow rate in the first few minutes, such as the profile shown in FIG. 3.
Particularly for aircraft, it would be desirable to provide a chemical oxygen generator that permits extension of the duration of operation of the chemical oxygen generator without increasing the weight or length of the generator. The present invention meets these and other needs.